1. Field of the Invention
The present invention relates to a suspension strut for a car in which a coil spring is integrated and assembled with a shock-absorber.
2. Background of the Related Art
FIG. 1 is a perspective view showing a conventional car suspension strut (laid-opened Utility Model publication No. 2000-16340).
As shown in FIG. 1, a car suspension strut 100 consists of a shock-absorber 110 for generating a damping force by reciprocating a valve in the interior of the shock-absorber within which oil is filled, and a coil spring 140′ located in the outside of the shock-absorber 110 in order to restore a compressed shock-absorber to the former state.
The shock-absorber 110 consists of an external case 111 for receiving the valve (not shown) and a rod 120 connected to the valve (not shown).
To connect a knuckle and a strut, a knuckle bracket 112 is mounted on the external case 111. A lower spring seat 150 is fixed to the external case 111 above the knuckle bracket 112. According to the fixed location of the strut, instead of the knuckle bracket 112, a cylindrical shaped bracket may be mounted on the lower portion of the external case 111.
A lower spring pad 152 consisting of rubber material rests above the lower spring seat 150 and a coil spring 140′ is mounted above the lower spring pad 152.
Also, an upper spring pad 162 is mounted above the coil spring 140 and then an upper spring seat 160 is inserted onto the rod 120 of the shock-absorber 110.
An insulator 130 is mounted on the upper spring seat 160 in such a manner that the upper spring seat 160 and the insulator 130 are fixed to the rod 120 of the shock-absorber by a nut 125. When the strut is installed in the front of a car, a bearing (not shown) may be installed in the inside of the insulator 130 so that the strut is rotated to a car body upon steering.
A bolt 132, mounted on the insulator 130, is a member fixing the strut 100 to the car body.
That is, the conventional suspension strut for the car has adopted a structure in which the lower spring seat 150 is fixed to the external case 111 of the shock-absorber through a welding and then the coil spring 140′ is installed in the lower spring seat 150. Accordingly, a portion (hereinafter, referred to as a bottom part) at which the coil spring 140′ is contacted to the lower spring seat 150 is necessary.
The bottom part is commonly set to 0.75 turns on the basis of the number of winding turns of the coil spring 140′. In the case that a lower spring pad 152 is installed between the coil spring 140′ and the lower spring seat 150, the bottom part is likewise included in the coil spring 140′.
Similarly, the coil spring 140 mounted on the conventional car suspension strut has a structure in which the coil spring includes a top part that contacts with the upper spring seat 160.
In the above-described conventional art, there was a problem in that the setting of the bottom part having 0.75 turns of a coil spring is required and a material cost of the coil spring is high since the bottom part does not provide a spring function.
Further, to avoid the coil being located at the region neighboring the bottom part from being contacted with the spring seat to generate a stress concentration when the coil spring is subject to an overload, a lower spring pad or an upper spring pad may be adopted. However, another problem is that the spring pad that receives the bottom part of the coil spring is enlarged in size, thereby increasing the manufacturing cost.